Methods and apparatus have been developed for the study of kidney and toad bladder epithelial cells on porous membranes. An important feature was the cementing of the membrane to a polycarbonate ring (1" I.D., 1' 1/4" O.D., 1/2) so that the membrane is attached to an electrical insulator which can operate the solutions contacting the two sides of the membrane. Chambers for potential difference, short circuit current and resistance measurements have been constructed to accommodate the ring. The clamping forces are exerted on the ring rather than the membrane. Solution circulating and gas exchange done separately with the aid of a small peristaltic pump. Chamber designs for sterile measurements have been constructed also.